The present invention relates to torque motors. Motors of this type typically provide angular displacement or movement of a rotor by an amount proportional to the characteristics of an electrical signal applied to the windings of the motor. For example, angular movement can be proportional to the voltage applied to the motor winding.
Torque motors have found widespread application in various control systems. In these systems it is desirable to rotate a shaft to a specific position or to apply a specified amount of torque to a shaft in response to an electrical control signal. In one particular system, it has been desirable to utilize a torque motor to control the position of a throttle plate within an internal combustion engine. One such system is described in Ser. No. 09/076,352, filed May 12, 1998, now U.S. Pat. No. 5,912,538, assigned to the assignee of this disclosure and incorporated here by reference is directed to breaking ice within a throttle assembly after a period of non-use. Another such system controls the position of the air inlet throttle valve by an electrical signal during engine operation.
With regard to controlling throttle plate position in an operating engine, older systems were directly mechanically controlled by user movement of a throttle linkage attached to the throttle valve. On the other hand, electrical throttle valve control is especially desirable in certain motor vehicle applications such as to provide cruise control and/or to override the user input to the throttle position control mechanism in response to extreme driving conditions or emergency situations. For example, where an anti-lock brake system, traction control system or yaw rate control system is employed on the vehicle, it is desired under certain conditions to have the electronic control system determine the throttle position rather than the operator.
A drawback exists however with respect to electrically controlled throttle systems. Namely, if the vehicle electrical system fails, or if electrical power to the throttle motor is interrupted, the electrical signal controlling the vehicle throttle position vanishes causing the throttle valve to "float." It has been appreciated in the art that a floating throttle may open further thus accelerating a vehicle unexpectedly or dangerously. In recognition of this danger, throttle control systems typically include springs to close a throttle valve in the absence of opening torque provided by the throttle controller mechanism or motor. However, this spring closure feature results in sharply diminished airflow to the vehicle motor causing the vehicle to slow and eventually to stop, perhaps in traffic, again potentially placing the occupants and nearby vehicles in danger.
The present invention contemplates a new, safer electronic throttle and method of use, which overcomes the above referenced problems and others.